For example, automatic analysis devices generally employ an non-sealed liquid holding container with the upper opening portion opened. In recent years, use of sealed liquid holding containers with the opening portion closed with a rubber plug, such as a vacuum blood collection tube, have become widespread. In dispensing devices, too, there is a demand for direct liquid collection without having to unplug the sealed holding container.
However, the inside of a sealed liquid holding container typically has a negative pressure relative to the external atmospheric pressure. When a lid has been opened and closed, or if sample injection into the container has been performed using a syringe, for example, the internal pressure may have become positive relative to the external atmospheric pressure. When there is a pressure difference between the inside and outside of the liquid holding container, as a probe is inserted into the liquid holding container, the flow passageway of the dispensing device as a whole connected to the probe may contract or expand due to a pressure variation, causing a movement of the liquid or gas in the flow passageway. In addition, when the probe is removed from the liquid holding container, the flow passageway may be deformed again by exposure to the atmosphere, causing a movement of the liquid or gas in the flow passageway, including a suctioned sample. As a result, the position of the suctioned sample in the probe may vary due to different internal pressures of the liquid holding container. This makes it impossible to obtain a constant amount of dispensed liquid relative to the amount of operation of a pump, and to achieve required dispensing accuracy.
Various measures have been taken to eliminate the pressure difference between the inside and outside of the liquid holding container. For example, a probe is provided with a thin tube for liquid sample suction and a thin tube for ventilation that are integrated (see Patent Literature 1). According to this technology, the probe equipped with the two passageways is passed through the rubber plug, and ventilation is performed via the ventilation passageway while liquid is suctioned via the suction passageway, thus eliminating the pressure difference between the inside and outside of the liquid holding container. In another example, an insertion hole for the sample collection probe is formed in the sample container plug using a perforating device equipped with a Z-shaped blade (see Patent Literature 2). According to this technology, as the sample collection probe is inserted, the opening or hole formed in the plug expands, whereby sufficient ventilation is provided, eliminating the pressure difference between the inside and outside of the liquid holding container.